The present invention generally relates to a humidification system and methods in conjunction with other environmental control systems for maintaining and controlling the humidity content in perishable goods containers during transport and holding. This invention further relates to a portable centralized master unit container for performing the humidification operations in one or more portable perishable goods containers.
It is generally well understood and widely accepted that it is desirable to prevent deterioration of the quality, quantity and appearance of consumable perishable goods, such as fresh fruits, vegetables, cheeses, meats, fish and the like, during lengthy transportation and holding operations, up to their final arrival in the global market.
Moreover, some foodstuffs, such as fruits and vegetables (e.g., broccoli) that must be shipped long distances to market (e.g., from Asia to North America) are shipped packed in crushed ice in the shipping container. As a consequence, less foodstuffs can be placed in the container because the crushed ice takes up part of the weight limit and available space in the container. The ice has been used not only for refrigeration, but also for humidification. Replacement of the crushed ice with a suitable system for a refrigerated and humidified atmospheric control allows for a significant increase (e.g., 30% to 50%) in the amount of foodstuffs that can be shipped in a container.
Preservation of moisture in perishable goods is a critical aspect of prevention of deterioration of perishable goods. Coyle et al. in U.S. Pat. No. 3,694,925 recognized this and understood that the actual process of refrigeration of perishable goods in railroad cars reduces the moisture content in the atmosphere around the goods, and within the goods, to an undesirable level. The solution proposed by Coyle et al. was to convey a portion of the condensed water from refrigeration to the intake of the circulating fan, while draining off the remainder of the water. This approach obviously resulted in considerable dehydration of the goods, and would not meet the current requirements of today""s markets.
Rainey, in U.S. Pat. No. 3,940,062, attempted to improve the situation by packaging moisture pods with the perishable goods in a stagnant environment.
Rhoad, in U.S. Pat. No. 3,961,925, devised a very elaborate means for spraying a recycled liquid coolant, such as chilled brine, directly onto the perishable goods during transportation and storage, to address the needs of cooling and humidification without success.
Rath, in U.S. Pat. No. 4,003,728, specifically targeted product spoilage through dehydration caused by refrigeration systems recycling dried air around the perishable goods. Rath provided an opportunity for condensate from the refrigeration system to be absorbed by the stream of circulated air. In this regard, Rath provided a humidity sensor in the ducted stream of air coming into the cargo container and passing through a duct along the bottom of the container and up through vents. This duct also contained condensate, and excess was disposed of through floor drains. The air moved upward around the goods and was collected by a return duct and passed into the front equipment section and downward through the refrigeration (or heating) unit. One problem with Rath""s approach is that if the relative humidity sensor reading dropped below the stated value (preferably 80% relative humidity), only an alarm would be lighted. Such an alarm was not likely to be seen deep in a cargo hold of a ship, or by a driver of a truck, or by a railroad engineer, and, if not seen, no positive action could be taken. A second problem was that the position of Rath""s moisture sensor was located only a few inches above the surface of water from condensation collected in the duct and quite likely never dropped below a reading of 80% relative humidity, regardless of a much lower humidity level around goods at the top or middle of the cargo. A third problem is that Rath notes excess water that collected in the duct was drained from the cargo container through a floor vent. Since this water came from the perishable goods, Rath""s process was also dehydrating the goods to a considerable extent. It is further noted that Rath""s system has poor humidity pick up from the surface of the water (i.e., negligible quantities of moisture would be reabsorbed by the circulating air stream) at the low temperatures the refrigerated perishable goods containers will operate, due to the low water vapor pressure and the relatively low surface area of the water-atmosphere interface.
Burg, in U.S. Pat. No. 4,655,048, describes a hypobaric preservation of non-respiring animal matter by contacting the storage atmosphere with a body of heated water and very carefully controlled pressures slightly less than the vapor pressure of water at the storage temperature in sealed containers. Such an approach simply is not practical for bulk transport and holding of perishable goods.
Edwards, in U.S. Pat. No. 4,808,303, describes a produce hydration system for use in display racks in which water is carefully filtered, pressurized and efficiently sprayed or misted over the surface of exposed produce in display racks. While providing interesting technology related to spraying, Edwards fails to teach how to maintain proper humidification during transportation and holding of perishable goods.
Wallace, in U.S. Pat. No. 4,884,411, describes a high humidity refrigeration apparatus that is fitted into one end of a shipping container. At the top of a vertical casing or duct is a water spray assembly. Below the casing or duct is a cooling section, below which is mounted a heating section, below which is a water reservoir. Water is pumped from the reservoir to the spray assembly from which it falls on the cooling section and then on to the heated section. Air enters this unit just above the water level in the reservoir, and passes upward over the heating section where it is warmed and can pick up humidity. The air is then passed up over the cooled section where it is cooled and excess water is condensed from the air and falls back to the reservoir. The air then continues upward past the spray assembly and on to the produce section in a horizontal direction and is brought off the top and is cycled back to repeat the process. Those familiar with thermodynamics will recognize the process could achieve saturated, cooled air if the flow rate of the air were slow enough relative to the size of the heating and cooling sections; however, the energy efficiency in doing so would be very poor and the capacity of the system would be limited to low demands for cooling and humidification. Transportation costs of perishable goods would be high because of the required large size and weight of the unit relative to the mass of cargo it can service.
Spruill, in U.S. Pat. No. 5,037,459, teaches the use of a quantity of a salt solution in communication with the atmosphere in a substantially closed container to maintain a desired level of humidity. The required bulk and weight of such a solution would be prohibitive for portable perishable goods containers in regards to both cost and space.
Coffield, in U.S. Pat. No. 5,127,233, teaches moisture recovery from compressed air by means of a filter. Such moisture is then supplied to the atmosphere around the foodstuffs. This method is energy inefficient, and is not the subject of the instant invention.
Podd et al., in U.S. Pat. No. 5,529,177, teaches the use of saturated desiccant panels for gradually releasing humidity in containers. This method is a very weight intensive approach to transportation containers, and lacks the immediate control for supplying humidity on demand.
Kleinberger et al., in U.S. Pat. No. 5,762,661, describes a way to refine a mist in a humidification system. Such refinements are not a part of the instant invention.
Fractal, Inc., according to their product specification sheet, offers a state-of-the-art humidification system using air atomization nozzles, oil-less food grade compressors and humidistat sensors that are accurate to plus or minus 2% up to 98% relative humidity. This system produce a humidity plume which is readily absorbed into the atmosphere and the system comes pre-assembled. However, the design of the system does not include certain environmental aspects that are included in the instant invention. Nor does the Fractal unit lend itself to the integrated design efficiencies and improvements of the instant invention. Further, the Fractal system is not designed to be portable or used in conjunction with shipping, cargo or transportation containers.
The Rath patent, U.S. Pat. No. 4,003,728 cited earlier, disclosed one step in an integrated system for environmental control of perishable goods during transportation. In this regard, Rath describes a plurality of portable individual containers connected to a central portable container which supplied electrical services to the individual cargo containers and monitored the temperature and humidity therein with a recording device. However, Rath does not contemplate or anticipate the design improvements embodied in the instant invention.
Herdeman et al., in U.S. Pat. No. 5,333,394, also describes a system which included a plurality of containers to be connected from time to time to a central source of controlled atmosphere which supplies a controlled atmosphere, gaseous by nature, to at least one of the shipping containers for perishable goods. This patent neither contemplates nor anticipates the improvement in total design efficiency of the instant invention which generates the required humidity source in the individual containers of perishable goods from a liquid source and can service the humidity needs of all attached containers simultaneously without having to assign priorities to specific containers.
Gast, Jr. et al, in U.S. Pat. No. 5,799,495, extends the teachings of the Herdeman et al. patent, U.S. Pat. No. 5,333,394, to a system for transporting and ripening perishable goods in which the oxygen and nitrogen content of individual perishable goods containers are controlled by delivering a specific composition of nitrogen and oxygen from a central atmospheric generation container to each of the attached perishable goods containers. In this patent, Gast, Jr. also extends the teachings of his earlier patent, U.S. Pat. No. 5,649,995, which used a nitrogen generation system to provide controlled levels of nitrogen and oxygen in a container for perishable goods. In neither of these patents does Gast, Jr. contemplate or anticipate the improvement in total design efficiency in the instant invention which generates the required humidity and control for further improving the environment for perishable goods during transportation, holding and ripening.
The present invention addresses these and other problems and deficiencies of prior art systems.
According to the present invention there is provided a centralized humidification container system comprising one or more containers to confine perishable goods in a humidity controlled environment, a portable master unit container which houses the controlling equipment with a source of humidification water, and includes means for connecting the master unit container to each of the perishable goods containers to pass information and fluid between the master unit container and each attached perishable goods container. This centralized humidification controlled container system is synergistic with other systems which control other aspects of the environment in the perishable goods container such as temperature, oxygen, carbon dioxide, nitrogen, ethylene, etc. or in also providing services to such containers such as electrical power. The centralized humidification controlled system of the present invention is used in conjunction with any such other system, either singly or in any combination, and is an improvement to previously known means of providing environmental control to perishable goods during transportation and holding.
In accordance with another aspect of the present invention, there is provided a commercial container for confining perishable goods for the purposes of transporting and holding, which contains equipment for thoroughly circulating the internal gaseous atmosphere around the perishable items by means of a system of ducts, vents and returns, and is adapted to include: (a) at least one spray nozzle capable of producing a fine atomized mist or atomized fog of water in the duct system, such that the flow of internal atmospheric gases can be increased in humidity content, (b) at least one sensing means for sensing the humidity content of the internal atmospheric gases, and (c) detection means for detecting whether the internal gaseous atmosphere is being circulated, and may optionally include (d) a condensate recycle line, which in each case is connected to the master unit container through an appropriate conduit.
The conduits may be grouped in various ways within different umbilical cords such as the conduits for fluids collected into a fluid umbilical cord and the conduits for information may be collected into a data umbilical cord, or they may be combined into a single umbilical cord (having one or more fluid lines and a data line), or in any other way which is appropriate. In this way, one or more containers of perishable goods are connected to the master unit container wherein information is processed to determine if a particular perishable goods container requires additional humidity and, if so, water is sprayed from a nozzle in a duct of that container, while the confined atmosphere is being circulated around the perishable items until the target humidity content in that container is achieved. At this point, the spray of water in the duct of that container is interrupted. Potable water that is treated by filtration is supplied to the nozzles from a reservoir located in the master unit container. The potable water may also be chemically treated to inhibit growth of bacteria and the like.
Condensate from a refrigeration system, sea water or other non-potable water can be processed by known means making it suitable for addition to the water reservoir. A manifold within the master unit container is used to direct water to one or more of the perishable goods containers simultaneously.
A centralized or distributed control system processes the information from all humidity sensors, compares the humidity levels to predetermined ranges, determines when the circulating system is operating in the perishable goods container, activates appropriate solenoids, switches, relays, valves, pumps, etc. spraying water only while the circulating system is operating and only to maintain the predetermined humidity limits within a particular container, and optionally can signal for service if a given aspect needs operator attention. In a distributed control system individual controllers can monitor and control such items as sensors and valves.
According to one aspect of the instant invention there is provided a simple and effective way of modifying commercially available portable refrigerated transportation containers currently used for shipping, railroads and trucking for transporting and holding perishable goods, to include humidification and management of the humidity levels for optimum results.
A second aspect of the instant invention collects the humidification support and management in one portable master container that can provide humidification services for one or more perishable goods containers based on existing commercially available components.
A third aspect of the instant invention is a miniaturized version of the master container which can be conveniently attached to the front of a modified existing refrigerated truck, independent of whether it is on the road or transferred to a flatbed rail carrier.
A fourth aspect of the instant invention integrates the novel humidification container system with any and all other known atmospheric control systems for transporting and holding perishable goods that are compatible with or utilize a centralized master unit container attached to one or more cargo containers.
It is an object of the instant invention to provide an improved efficiency humidification system for use in transportation and holding, including ripening operations, of perishable goods in portable containers through use of a master unit distribution container connected to at least one container for perishable goods.
A second objective is to have this improved design synergistic with all state-of-the-art methods and equipment for controlling and maintaining all other atmospheric environments known or anticipated to be useful in transporting and holding perishable goods until they reach global markets.
Another objective of the instant invention is to maximize net value to shippers who need only make minor modifications to existing perishable goods containers to accommodate humidification in concert with a master unit container.
Another objective of this instant invention is to provide a humidification system integrated with other atmospheric control systems for perishable goods being transported or kept in holding, as well as integration into new improved system designs not previously described or contemplated.
A further objective of the instant invention is to maximize the use of the equipment located in the master container unit by having it cycled to a new shipment while actual empty cargo containers are frequently left at some distant location for some time.
A further objective of the instant invention is to provide improved quality and increased quantity of perishable goods to the global markets at reduced cost compared to current methods.
Still other objectives and advantages of the present invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description, accompanying drawings and appended claims.